Machining unit application control apparatus and method employing data from several different operations

ABSTRACT

In an application control apparatus or method for a machining unit such as an electric discharge machine, a plurality of methods of realizing desirable machining states such as those on machining know how techniques are independently described and stored as knowledge, and control is carried out according to the methods thus stored, whereby the machining unit is maintained in desirable state at all times.

TECHNICIAL FIELD

This invention relates to application control apparatuses for a varietyof machining units (hereinafter referred to as "machining unitapplication control apparatuses", when applicable), and moreparticularly to a machining unit application control apparatus in whicha plurality of method of obtaining desirable machining states such asthose on machining know how techniques are stored as knowledge basesindependently, and desirable machining states are held with ease byperforming controls according to the methods thus stored.

The invention relates further to a machining unit application controlapparatus in which methods can be readily added, and modified, and whichcan be used by a plurality of machining units in common.

The invention relates further to a machining unit application controlapparatus which, in an electric discharge machining operation, maintainsthe discharge machining condition most suitable, and realizes thejumping operation of a machining electrode in such a manner as tomaximize the discharge machining efficiency.

The invention relates to a machining unit application control apparatusin which, during machining methods of an operator are collected, and anautomatic machining operation is carried out according to the machiningmethods thus collected.

The invention relates further to an automatic positioning control devicefor an electric discharge machine, and more particularly to a machiningunit application control apparatus in which a plurality of methods arestored to realize most suitable positioning procedures, for instance,according to operator's know how techniques concerning positioningoperations, and to perform automatic positioning decision with highaccuracy, and an automatic positioning operation is carried outaccording to the methods thus stored, whereby it is achieved accuratelyat all times.

The invention relates further to an machining unit application controlapparatus which operates for determination of a machining operationcompletion in an electric discharge machine in which a machiningelectrode is moved in a direction in which the electrode is pushed intoa workpiece, and in directions perpendicular to the aforementioneddirection.

BACKGROUND ART

An electric discharge machine will be described which is one of theaforementioned variety of machining units.

FIG. 1 is an explanatory diagram showing the arrangement of anapplication control apparatus for an electric discharge machine whichhas been disclosed by Japanese Patent Application Publication No.10769/1987 for instance. In FIG. 1, reference numeral 1 designates amachining electrode; 2, a workpiece to be machined; 3, a machiningvessel; 4, a machining solution; 5, a spindle; 6, a drive motor; 7, aspeed or position detector; 20, a machining unit; 21, an electrodeposition control section; 22, a machining power source; 23, a staterecognizing section; and 31, an application control section. In thisdescription, the term "machining unit" is intended to mean that whichincludes the above-described parts 1 through 7, and 21 and 22.

The operation of the application control apparatus thus constructed willbe described. First, the operator determines initial machiningconditions taking into account the material and size of a workpiece tobe machined, machining quantity, finish accuracy, and so forth, and setsthem for the machining unit 20. For instance, the operator sets thepeak, pulse width and pulse interval of a pulse current, an electrodepull-up period, an electrode pull-up distance, electrode servoparameters, etc.

After the initial machining conditions have been set, a dischargemachining operation is started. That is, the machining power source 22applies the pulse voltage across the inter-electrode space (or dischargegap) between the machining electrode 1 and the workpiece 2 to induceelectric discharges, whereby the workpiece 2 is machined with theelectrode 1 which is moved relative to the workpiece 2. The electrodeposition control section 21 compares an average inter-electrode voltageprovided by the state recognizing section 23 with a reference voltage,to control the position or speed of the machining electrode 1 thereby tomaintain a suitable distance between the machining electrode 1 and theworkpiece 2.

In an electric discharge machining operation, the distance between themachining electrode 1 and the workpiece 2 (hereinafter referred to as"an inter-electrode space or discharge gap", when applicable) isgenerally small, ten microns to several tens of microns. Therefore, inthe case where the machining area is large, it is relatively difficultfor the waste material such as sludge formed during discharge machiningto flow through the inter-electrode space. As a result, an abnormalelectric discharge is liable to occur. That is, the waste material staysin the inter-electrode space, so that electric discharges are inductedcollectively at the position of the waster material. This difficultyattributes to the fact that, during electric discharge machining, wastematerial such as sludge is formed more than removed. The difficulty maybe eliminated by the following method: The abnormal condition isdetected or predicted, to suppress the production of waste material, orto accelerate the removal of waste material.

FIG. 2 shows the variations in position of the machining electrode 1.More specifically, the part (a) of FIG. 2 shows the variation inposition of the machining electrode in the case where a normal electricdischarge machining operation is carried out; whereas the part (b) ofFIG. 2 shows the variation in position of the machining electrode in thecase where the abnormal condition occurs in the inter-electrode space.During electric discharge machining, the machining electrode 1 isvibrated with an amplitude of 10 to 100 microns. In a normal electricdischarge machining operation, the point 101 where the downward movementof the machining electrode is changed to the upward movement(hereinafter referred to "a minimum point 101", when applicable) ismoved downwardly gradually as the discharge machining operationadvances; whereas when the abnormal condition occurs in theinter-electrode space, the minimum point 101 is moved upwardly.Therefore, upon detection of the upward movement of the minimum point101, by decreasing the pulse width of the pulse current supplied by themachining power source 22, the formation of waste material such assludge in the inter-electrode space can be suppressed; and by increasingthe periodic electrode pull-up distance, the removal of waste materialfrom the inter-electrode space can be accelerated.

In FIG. 1, the state recognizing section 23 detects the minimum point101 from the variation in position of the machining electrode 1, andinforms the application control section 31 of the upward or downwardmovement of the minimum point 101. When the upward movement of theminimum point 101 exceeds a predetermined threshold value, theapplication control section 31 determines that the abnormal conditionhas occurred in the inter-electrode space, and applies an instructionsto the electrode position control section 21 to increase the electrodepull-up distance to accelerate the removal of the waste material or tothe mechining power source 22 to decrease the pulse width of the pulsecurrent to suppress the formation of waste material.

FIG. 3 is a circuit diagram of the application control section. Theapplication control section applies an instruction 111 to the electrodeposition control section 21 to increase the electrode pull-up distancewhen the level of the minimum point 110 detected by the staterecognizing section 23 exceeds a predetermined threshold value.

Another example of the conventional machining unit application controlapparatus will be described.

FIG. 4 is a block diagram showing the conventional machining unitapplication control apparatus which has been disclosed by JapanesePatent Application (OPI) No. 297017/1986 (the term "OPI" as used hereinmeans an "unexamined published application") for instance. In FIG. 4,reference numeral 51 designates a discharge machining process includingan electric discharge phenomenon; 52, the amount of state of thedischarge machining process; 53, an electrode control system; 54, aninter-electrode distance between a machining electrode and a workpiecewhich is controlled by the electrode control system; 55, a statedetector for detecting the amount of state; 56, a detection valueprovided by the state detector 55; 57, an instruction value setting unitfor setting the state of the discharge machining process; 58, aninstruction value provided by the instruction value setting unit 57; 59,a difference value obtained from the instruction value 58 and thedetection value; 60, a jump controlling unit for controlling a jumpingoperation; 61, an amount of jump operation; 62, a switching unit fortselecting an inter-electrode distance control according to thedifference value 59 or a jumping operation according to the amount ofjump; 63, an amount of operation which the switching unit 62 applies tothe electrode control system 53; 64, a machining electrode positionsignal; 65, a jump setting unit for setting an amount of jump or aperiod of jump according to a machining depth in advance in order toperform a suitable jumping operation; and 66, a jump instruction valuewhich the jump setting unit 65 applies to the jump controlling unitaccording to the machining electrode position signal 64.

In FIG. 1 the mechanical part of the machining unit is represented bythe parts (1) through (7), whereas in FIG. 4 it is represented asobjects to be controlled which are an inter-electrode distance inputtedand an amount of machining state outputted.

An inter-electrode distance control operation will be described withreference to FIG. 4. In FIG. 4, the difference value 59 is obtained fromthe instruction value 58 provided by the instruction value setting unit57 which sets a desirable state for the discharge machining process andthe detection value 56 provided by the state detecting unit 55 whichdetects the state of the discharge machining process. The differencevalue 59 thus obtained is applied through the switching unit 62, as theamount of operation 63, to the electrode control system 53. Theelectrode control system 53 operates to adjust the inter-electrodedistance 54 so that the difference value 59 be zeroed. Thus, desirabledischarge machining conditions are maintained at all times.

However, as the discharge machining operation advances, the wastematerial formed is caused to stay in the inter-electrode gap between themachining electrode and the workpiece, as a result of whichshort-circuit occurs in the inter-electrode gap frequently. Hence, it isdifficult to maintain the electric discharge machining operation stablemerely by the above-described inter-electrode distance control.

Therefore, in general, a pumping action attributing to the jumpingoperation of the machining electrode is utilized to remove the wastematerial from the inter-electrode gap between the machining electrodeand the workpiece.

The term "jumping operation" as used herein is intended to mean theperiodic operation that, during inter-electrode gap control, themachining electrode is forcibly pulled up a predetermined distance fromits machining position irrespective of the instruction value 58 or thedetection value 56 and is then returned to the original machiningposition.

The jumping operation of the machining electrode is controlled asfollows: Jumping conditions such as an amount of jump which is anelectrode pull-up distance determined according to a machining depth anda period of jump which is an electrode pull-up period are set for thejump setting unit 65 in advance. A machining depth is obtained from theposition signal 64 of the machining electrode which is in operation, andthe jump instruction value 66 is transmitted to the jump controllingunit 60 referring to the jumping conditions set in the jump setting unit65, as a result of which the jump controlling unit 60 applies the amountof jump operation 61 through the switching unit 62, as the amount ofoperation 63, to the electrode control system 53.

As is apparent from the above description, the machining electrodejumping operation is essential for maintaining the electric dischargemachining operation stable at all times; however, in view of machiningefficiency, it can be said that the jumping operation does notcontribute directly to the machining of the workpiece. Thus, in order toimprove the machining efficiency, it is essential to perform the jumpingoperation of the machining electrode most suitably.

In order to realize the most suitable jumping operation of the machiningelectrode, it is necessary to determine the jumping conditions such asan amount of jump and a period of jump not only from a machining depthbut also a machining electric power source's pulse conditions, amachining electrode configuration, the materials of a machiningelectrode and a workpiece, and so forth. Thus, in general, the jumpingoperation is carried out by a person skilled in the art. That is, such askilled person monitors a discharge machining operation, to change thejumping operation suitably according to the degree of instability of thedischarge machining operation.

The conventional machining unit application control apparatus isconstructed as described above. Therefore, the change of the electrodepull-up distance is determined merely from the result which is providedaccording to the method in which the electrode pull-up distance isincreased when the amount of rise of the minimum point exceeds apredetermined threshold value. Therefore, it is difficult to realize thejumping control according to an intricate method such as a methodexpressed vaguely by the skilled person. This is a first problemaccompanying the conventional machining unit application controlapparatus.

The conventional machining unit application control apparatus isorganized as described above. Therefore, in order to add another methodof controlling an electrode pull-up distance or to change the method, itis necessary to change the hardware realizing the method. And in thecase where the method is realized by software, the software fordetermining the electrode pull-up distance according to the method mustbe modified in its entirety. It is impossible to readily add or changethe know how possessed by the manufacturer or user. Furthermore, inorder to allow a plurality of machining units to hold a variety of knowhow in common, it is necessary to allow them to have in common not onlythe method but also hardware or software for realizing the method.Satisfying this requirement takes time and labor. This is a secondproblem accompanying the conventional machining unit application controlapparatus.

The conventional machining unit application control apparatus thusconstructed suffers from the following difficulties: In setting jumpingconditions according to the method provided by the person skilled in theart to perform a most suitable jumping operation, it is difficult tosuitably express as jumping conditions the qualitative and valueexpression included in the method. In order to automatically change thejumping operation according to the degree of instability of thedischarge machining operation (without the skilled person) it isdifficult to correctly describe the standard of decision on which theskilled person determines the degree of instability. Thus, it is ratherdifficult to improve the discharge machining efficiency. This is a thirdproblem accompanying the conventional application control apparatus.

In the conventional application control unit thus organized, it isdifficult to modify an operator's machining method. In addition, incollecting an operator's machining method, it is necessary to reveal themachining conditions for which the operator starts operations and theoperations done by him. This is a fourth problem accompanying theconventional apparatus.

FIG. 5 is an explanatory diagram showing the arrangement of anotherexample of the conventional electric discharge machine. In FIG. 5,reference numeral 1 designates a machining electrode; 2, a workpiece tobe machined; 3, a machining vessel; 4, a machining solution; 5, aZ-axis; 6, a drive motor; 7, a speed and position detector; 8 and 9, anX-axis and a Y-axis, respectively; 10 and 11, an X-axis drive motor, anda Y-axis drive motor, respectively; 12 and 13, speed and positiondetectors for the X-axis drive motor and Y-axis drive motor,respectively; 21, an electrode position control section; 22, a machiningelectric power source; 23, a detection value processing sectioncorresponding to the state recognizing section in FIG. 1; 31, anapplication control section comprising a numerical control unit(hereinafter referred to merely as "an NC unit", when applicable); 32, aCRT and a keyboard; 32, an I/O unit such as a paper tape reader.

The operation of the machine thus organized will be described. Anautomatic positioning operation is carried out as follows: The NC unit31 applies an instruction to the machining electric power source unit 22so that the latter outputs a DC low voltage different from that which isused for discharge machining; and the NC unit applies an instruction tothe electrode position control section 21 so that the latter 21 operatesto move the electrode in a specified direction along a specified axis.When the contact of the electrode with the workpiece 2 is detected bythe detection value processing section 23, the NC unit 31 suspends theapplication of the instructions to the machining electric power sourceunit 22 and the electrode position control section 21. Thus, theautomatic positioning operation has been accomplished.

The automatic positioning function is one of the fundamental functionsof the NC unit 31. The operator determines the relative position of theelectrode 1 and the workpiece 2, or measures the displacement of theelectrode from the center by using the automatic positioning function incombination. The determination of the relative position of the electrodeand the workpiece and the measurement of the displacement of theelectrode from the center is carried out according to a positioningprocedure which is considered best through the past experience of theoperation, because the positioning procedure cannot be determinedunivocally depending on the configurations and reference values of theelectrode and the workpiece. Furthermore, whether or not the result ofthe automatic positioning operation carried out by the NC unit 31 isacceptable is determined according to the past experience of theoperator, the average value of the results of a plurality of automaticpositioning operations, the deepest value in a plurality of automaticpositioning operations, and the same value obtained continuously inseveral automatic positioning operations.

In the case where the electrode 1 and the workpiece 2 are equal inconfiguration and in reference surface, the positioning procedure is, ingeneral, programmed by NC program for execution. On the other hand, itcannot be determined by the operator whether or not the result of theautomatic positioning operation is acceptable; that is, thedetermination is carried out by utilizing the automatic positioningfunction of the NC unit. Therefore, if, in the automatic operation, thereference surface is smudged by some external disturbance duringpositioning or measuring, it is impossible to obtain the result of thepositioning or measuring operation with high accuracy. In thepositioning procedure, the automatic positioning feed speed andfrequency belong to the know how of the operator.

The conventional automatic positioning control apparatus thusconstructed suffers from the following difficulties: The operator mustspecify the positioning procedure for the NC unit, and he cannot bedetermine whether or not the result of the automatic position operationis acceptable; that is, the determination is carried out by utilizingthe automatic positioning function of the NC unit. The operator's knowhow of the electrode positioning and measuring method is not reflectedonto the automatic operation. This is a fifth problem accompanying theconventional apparatus.

Heretofore, in an electric discharge machining operation, the electrodeand the workpiece are moved relative to each other in such a manner thatthe former is pushed into the latter, and the distance between theelectrode and the workpiece in that direction is maintained constant byservo technique. Furthermore, in order to perform both a rough machiningoperation and a finish machining operation with one electrode, theelectrode or the workpiece are moved in a direction perpendicular to theordinary direction of feed; i.e., swinging motion is given to theelectrode or workpiece.

A control method for the movement in the direction in which theelectrode is pushed into the workpiece has been disclosed by JapanesePatent Application Publication No's. 19371/1986, 19372/1986, 19373/1986,19374/1986, and 58256/1986 for instance.

With respect to the swinging motion, the control method for the movementin the direction in which the electrode is pushed into the workpiecewill be described. In a first example of the control method, theelectrode is swung a predetermined number of times when it reaches adesired position in the direction in which the electrode is pushed intothe workpiece (hereinafter referred to as "an electrode pushingdirection", when applicable), and then it is moved in the electrodepushing direction. In a second example of the control method, after thelapse of a predetermined period of time from the time instant that theelectrode reaches the above-described desired position is detected withthe difference between the discharge machining voltage and the referencevoltage in a predetermined range, the electrode is moved in theelectrode pushing direction. In a third example of the control method,after the lapse of a predetermined period of time from the time instantthat the electrode reaches the above-described desired position isdetected with the distance for which the electrode is moved back andforth by inter-electrode voltage serve being in a predetermined range.

In the above-described first, second and third control methods, themovement of the electrode is utilized for decision of the accomplishmentof the machining operation; more specifically, it is used to determinewhether or not, with the electrode reached the desired position, theworkpiece has been machined uniformly to desired dimensions.

In the conventional discharge machining operation, the movement of theelectrode in the direction in which the electrode is pushed into theworkpiece is controlled as described above. Therefore, even whenmachining circumferences or machining environments are changed byvariations of various factors such as the area and configuration of anelectrode, machining depth, the configuration of revolution, machiningconditions, the presence or absence of a jet stream of machiningsolution, the decision of the accomplishment of the machining operationis carried out in the same manner, as a result of which the machiningaccuracy is not uniform. For instance in the case where the jet streamof machining solution is used, the waster material such as sludge formedduring machining is removed with high efficiency, and therefore thedistance between the electrode and the workpiece may be relativelysmall. On the other hand, in the case where the jet stream of machiningsolution is not utilized, the ability of removing the waste materialfrom the inter-electrode gap is low, and secondary electric dischargeoccurs through the waste material, thus increasing the inter-electrodegap between the electrode and the workpiece. Hence, if, when a pluralityof workpieces are machined the same depth, for all the workpieces thusmachined the accomplishment of the machining operation is decided in thesame manner, then the workpiece machined without the jet stream ofmachining solution is relatively large in dimension; whereas theworkpiece machined with the jet stream of machining solution isrelatively small in dimension. This is a sixth problem accompanying theconventional apparatus.

DISCLOSURE OF THE INVENTION

A first object of this invention is to solve the above-described firstproblem. More specifically, the first object is to provide a machiningunit application control apparatus with which an amount of operation canbe determined according to a plurality of methods, and the methods canbe readily added and modified, whereby machining know how techniques ofoperators can be utilized for automatic machining operations forinstance.

A second object of the invention is to solve the above-described secondproblem. More specifically, the second object is to provide a machiningunit application control apparatus with which automatic machiningoperations or the like can be achieved according to intricate methodssuch as those on machining know how techniques of operators, and themethods can be readily added and modified and can be used by a pluralityof machining unit in common.

A third object of the invention is to solve the above-described thirdproblem. More specifically, the third object is to provide a machiningunit application control apparatus with which methods of skilledoperators concerning jumping conditions effective in performing ajumping operation most suitably and a reference for determination of adegree of instability in a discharge machining operation can be writtenwith ease, and the methods are effectively used for automaticallyperforming or changing a jumping operation with high accuracy.

A fourth object of the invention is to solve the above-described fourthproblem. More specifically, the fourth object is to provide a machiningunit application control apparatus with which an automatic machiningoperation can be performed according to machining methods of operators,and the machining methods can be collected and corrected with ease.

A machining unit application control apparatus, according to a firstaspect of the invention, comprises: a knowledge memory section in whicha plurality of methods of changing machining states are written; astatus memory section in which present and/or past machining statesand/or machining conditions are stored; and an inference section forcombining a plurality of results provided according to the machiningstates and/or machining conditions stored in the status memory sectionand the method concerning the statuses which are stored in the knowledgememory section, to obtain machining conditions for better machiningstates.

A machining unit application control apparatus according to a secondaspect of the invention comprises: a knowledge memory section in which aplurality of methods of changing machining states are written accordingto a rule consisting of a front condition part describing a condition tobe determined and a rear condition part describing contents to becarried out when the condition is satisfied or not satisfied; a statusmemory section in which present and/or past machining states and/ormachining conditions are stored; and an inference section for inferringmachining conditions for better machining states from statuses stored inthe status memory section and the methods stored in the knowledge memorysection,

In an electric discharge machining control apparatus according to athird aspect of the invention, methods effective in performing thejumping operation of the machining electrode are stored, present or pastmachining statuses required for the methods are detected by a statusdetecting unit, the detection values are stored in a status memorysection, an inference section operates to combines the results providedaccording to the methods stored in the knowledge memory section and thestatuses stored in the status memory section, whereby instructions forperforming a most suitable jumping operation or appropriately changingit are applied to a jump controlling unit.

A machining unit application control apparatus according to a fourthaspect of the invention includes a first arrangement group whichcomprises: a knowledge memory section in which methods of changingmachining conditions are written; a state recognizing section fordetecting machining states and processing signals; a status memorysection in which machining states provided by the state recognizingsection and/or set machining conditions are stored; and an inferencesection for obtaining machining conditions for better machining statesaccording to the machining states and/or machining conditions stored inthe status memory section and the methods concerning the statuses whichare stored in the knowlege section; and a second arrangement group whichcomprises: time-series data recording section for recording time-seriesdata including the set machining conditions, the machining statesprovided by the state recognizing section and machining conditionchanging operations performed by an operator; and a knowledge renewingsection for extracting a machining method from the contents of thetime-series data recording section, to renewing or correcting themethods stored in the knowledge memory section.

In the machining unit application control apparatus according to thefirst aspect of the invention, the inference section operates tocombines the operating data provided according to a plurality of methodssuch as methods which are described vaguely by skilled operators, tosuitably perform a machining operation according to intricate machiningknow how techniques, and the methods are stored in the knowledge memorysection independently of the inference section whereby the methods canbe added or modified with ease.

In the machining unit application control apparatus according to thesecond aspect of the invention, the methods of changing machining statesare written in the knowledge memory section according to thepredetermined rules and are made independent of the inference section,whereby machining know how techniques of skilled operators can bemodified by a manufacture or user or can be used by a plurality ofmachining units in common; and the inference section can determinemachining conditions for excellent machining states according tointricate machining know how techniques.

In the apparatus according to the third aspect of the invention, themethods including qualitative and vague expressions made by skilledoperators which are effective in allowing the machining electrode tojump most suitably are appropriately and readily written in theknowledge memory section, so that the inference section collectivelydetermines execution of a most suitable jumping operation andappropriate change of it according to the methods written in theknowledge memory section and the statuses which are detected by thestatus detecting unit with respect to the methods and stored in thestatus memory section.

In the apparatus according to the fourth aspect of the invention,normally the machining methods of skilled operators stored in theknowledge memory section of the first arrangement group are used forinference of machining conditions according to machining statuses sothat the machining unit operates in desirable state, whereby themachining operation is carried out as performed by a skilled person.

When, in the apparatus according to the fourth aspect of the invention,machining methods of skilled operators are collected or corrected, thefirst and second arrangement groups are used. That is, the machiningoperation is carried out with part or all of the machining conditionsmodified by the operator without use of the output of the inferencesection. After the machining operation has been accomplished, themachining method used is extracted, and the machining methods stored inthe knowledge memory section are modified suitably according to themachining method thus extracted. Thus, the machining methods of skilledpersons stored in the knowledge memory section are improved, thuspromising better control for the machining unit.

A fifth object of the invention is to solve the above-described fifthproblem. More specifically, a fifth object of the invention is toprovide an automatic positioning controlling device in which anautomatic positioning speed and automatic positioning frequency are mostsuitably determined from a plurality of positioning procedures accordingto the configuration, reference surface, etc. of an machining electrodeand workpiece, and the acceptability of the results of the automaticpositioning operation can be checked under the same rules as those usedby skilled persons.

The fifth object of the invention has been achieved by the provision ofan automatic positioning control device for an electric dischargemachine which, according to the invention, comprises: a memory sectionwhich stores a plurality of positioning procedures and a plurality ofmethods of determining whether or not the result of an automaticpositioning operation is acceptable; and a logic section for determiningan automatic positioning completion position and amounts of operationsprovided by the plurality of procedures. In the automatic positioningcontrol device, the logic section operates to combine the amounts ofoperations provided by the plurality of procedures, thereby to realizean automatic positioning operation on intricate know how techniques.Furthermore, the results provided by the plurality of methods arecombined, to determine the automatic positioning completion positionwith higher accuracy. In addition, the memory section stores thepositioning procedures and the methods of determining whether or not theresult of an automatic positioning operation is acceptable,independently of the logic section, with the result that the methods canbe readily modified.

A sixth object of the invention is to solve the above-described sixthproblem. More specifically, a sixth object of the invention is toprovide a method of utilizing machining environmental conditions such aselectrode configurations, machining solution jetting methods andmachining depths to determine the completion of a machining operationwith high accuracy, and to provide a machining operation completiondetermining apparatus for practicing the method.

In order to achieve the sixth object of the invention, an electricdischarge machining operation completion determining method is providedfor an electric discharge machining method in which an electrode and aworkpiece are moved relative to each other in such a manner that theelectrode is pushed into the workpiece, and a machining operation iscarried out while the distance between the electrode and the workpiecein the direction of movement of the electrode being maintained constantby servo control, and while the electrode or workpiece being oscillatedin directions perpendicular to the direction of movement of theelectrode. In the method, according to the invention, machiningenvironmental factors including machining solution jet pressure,machining area, machining depth and oscillation radius are detected andanalyzed, to determine machining operation completion determiningparameters including a range of difference between discharge machiningvoltage and reference voltage, and a duration time within the range ofdifference, and determination of the completion of a machining operationis carried out according to whether or not the machining operationcompletion determining parameters are satisfied by detection valuesprovided during machining.

Furthermore, in order to achieve the sixth object of the invention, anelectric discharge machining operation completion determining apparatusis provided for an electric discharge machine for practicing theabove-described electric discharge machining method. The apparatus,according to the invention, comprises: a first memory section in which aplurality of methods concerning detection and analysis of machiningenvironmental factors including machining solution jet pressure,machining area, machining depth and oscillation radius; a second memorysection which stores present and/or past machining states and machiningenvironmental conditions; and a logic section for combining a pluralityof results provided according to the machining states and machiningenvironmental conditions stored in the second memory section and theplurality of methods stored in the first memory section, to obtain amachining operation completion determining parameter, and to determine amachining operation completion according to the parameter.

In the electric discharge machining operation completion determiningmethod thus organized, a plurality of machining environmental factorssuch as machining solution jet pressure, machining area, machining depthand oscillation radius are detected and analyzed to determine machiningoperation completion determining parameters according to the machiningenvironmental factors. Hence, the completion of a machining operationcan be accurately determined according to whether or not the machiningoperation completion determining parameters are satisfied by detectionvalues provided during machining.

In the electric discharge machining operation completion determiningapparatus for practicing the above-described method, the logic sectionoperates to combine a plurality of results provided according to thepresent and/or machining states and machining environmental conditionsstored in the second memory section and the plurality of methodsconcerning detection and analysis of the machining environmental factorsstored in the first memory section, to obtain a machining operationcompletion determining parameter. Hence, even in an intricate machiningmode, the completion of a machining operation can be determined withhigh accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing the arrangement of one exampleof a conventional machining unit application control apparatus.

FIGS. 2a and 2b are explanatory diagrams for a description of themovements of a machining electrode.

FIG. 3 is a circuit diagram showing an application control section.

FIG. 4 is a block diagram showing another example of the conventionalmachining unit application control apparatus.

FIG. 5 is an explanatory diagram showing one example of a conventionalelectric discharge machine.

FIG. 6 is an explanatory diagram showing the arrangement of a machiningunit application control apparatus, one embodiment of the invention.

FIG. 7 is an explanatory diagram for a description of methods ofcontrolling an electrode pull-up distance.

FIG. 8. is a flow chart for a description of a method of obtaining anelectrode pull-up distance.

FIG. 9 is an explanatory diagram for a description of methods ofcontrolling an electrode pull-up distance according to a rule.

FIG. 10 is an explanatory diagram for a description of methods ofcontrolling an electrode pull-up distance according to a rule which isexpressed according to the fuzzy set theory.

FIG. 11 is an explanatory diagram indicating fuzzy set with membershipfunction.

FIG. 12 is an explanatory diagram for a description of electrode pull-updistance controlling methods according to rules.

FIG. 13 is a block diagram showing an electric discharge machiningcontrol apparatus, a third embodiment of the invention.

FIG. 14 is an explanatory diagram showing examples of a method ofeffectively permitting the jumping operation of a machining electrode.

FIG. 15 is an explanatory diagram showing the methods of FIG. 14 whichare expressed according to the fuzzy set theory.

FIG. 16 is an explanatory diagram showing the process of fuzzy inferencewith respect to the methods shown in FIG. 14.

FIG. 17 is a block diagram showing the arrangement of a machining unitapplication control apparatus, a fourth embodiment of the invention.

FIGS. 18a-18c and 19a-19b are explanatory diagrams for a description ofthe operation of the apparatus shown in FIG. 17.

FIGS. 20 and 21 are flow charts for a description of the operation ofthe apparatus shown in FIG. 17.

FIGS. 22, 23 and 24 are block diagrams showing arrangements of machiningunit application control apparatuses which are fifth, sixth and seventhembodiments of the invention, respectively.

FIGS. 25 through 30 are provided for another embodiment of theinvention. More specifically,

FIG. 25 is a diagram showing the arrangement of an electric dischargemachine.

FIGS. 26a and 26b are graphical representations showing the contents ofa first memory section including methods of determining an automaticpositioning speed and an automatic positioning frequency.

FIG. 27 is a flow chart for a description of the operation of processingan automatic positioning speed and an automatic positioning frequencyaccording to the contents of the first memory section.

FIG. 28 is an explanatory diagram showing data on an electrode and aworkpiece which are written in a second memory section.

FIG. 29 is a graphical representation showing the contents of the firstmemory section including methods of determining whether or not anautomatic positioning completion position is acceptable.

FIG. 30 is a flow chart for a description of a process of determiningthe completion of an automatic positioning operation or requiring there-execution of the automatic positioning operation according to thedegree of confidence on an automatic positioning operation completionposition.

FIG. 31 is a block diagram showing an electric discharge machiningoperation completion determining apparatus, another embodiment of theinvention.

FIGS. 32a-32c are explanatory diagrams showing one method of detectingand analyzing the machining environmental factors stored in a firstmemory section; more specifically, examples of a method of obtaining arange of difference between discharge machining voltage and referencevoltage which is one of the machining operation completion determiningparameters.

FIGS. 33a-33c are explanatory diagrams showing another method ofdetecting and analyzing the machining environmental factors stored inthe first memory section; more specifically, examples of a method ofobtaining a duration time within the range of difference which isanother of the machining operation completion determining of parameters.

FIG. 34 is a flow chart for a description of a method of obtainingmachining operation completion determining parameters by a logicsection.

FIG. 35 is a flow chart showing a machining operation completiondetermining method practiced by the logic section.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of this invention will be described with reference toFIG. 6

In FIG. 6, reference numerals 1 through 23 designates the same items asthose in FIGS. 1 through 5 showing the conventional apparatusesdescribed before; 31a, an application control section; 41, a statusmemory section; 42, a knowledge memory section; and 43, an inferencememory section.

The operation of the embodiment thus organized will be described.Several methods of determining an electrode pull-up distance as shown inFIG. 7 are stored in the knowledge memory section 7. In method 1,similarly as in the prior art, increase of the electrode pull-updistance is determined from the rise of the minimum point. Heretofore,the presence or absence of increase is determined merely by referring tothe threshold value; whereas in the invention, the method is stored inthe knowledge memory section 42 by means of software, and therefore themethod stored therein can be more intricate. In method 2, the electrodepull-up distance is controlled according to the distribution densityvariation rate of the time of period (hereinafter referred to as"no-load time", when applicable) which elapses from the time instantthat a pulse voltage is applied across the electrode and the workpieceuntil electric discharge starts. The methods may be stored in theknowledge memory section 42 by using hardware such as operationalamplifiers and switches instead of software.

FIG. 8 is a flow chart showing a procedure of obtaining an increase ordecrease of the electrode pull-up distance by using the methods storedin the knowledge memory section 42 and the machining statuses andmachining conditions stored in the status memory section 41. First, theinference section 43 reads method 1 from the knowledge memory section42, to obtain an increase or decrease Z₁ of the electrode pull-updistance in method 1 according to the degree of rise of the minimumpoint which has been stored in the status memory section 41 (Steps S31through S34). Similarly, according to method 2, an increase or decreaseZ₂ of the electrode pull-up distance in method 2 is obtained accordingto method 2 and the distribution density variation rate of the no-loadtime (Steps S35, and S32 through S34).

In the embodiment, N=2, and therefore the result of Step S35 is "YES".Two results obtained by the two methods are combined, to determine anincrease or decrease Z_(t) of the electrode pull-up distance, which isapplied to the electrode position control section 21 and the machiningelectric power source 22 (Steps S35 through S37).

In this connection, the following equation (1) may be utilized toaverage the results obtained by the methods: ##EQU1##

In the case of method 2, it is necessary to obtain the distributiondensity variation rate of the no-load time. It can be obtained asfollows: In the detection value processing section 23, the no-load timeis measured for a predetermined interval. By using the no-load time thusmeasured, a distribution density variation rate is calculated accordingto equation (5) shown in FIG. 7, and stored in the status memorysection. In the case of method 1, it is necessary to obtain the degreeof rise of the minimum point. In this case, it is obtained in thedetection value processing section 23, and stored in the status memorysection 41.

Thus, by obtaining a machining condition (increase or decrease of theelectrode pull-up distance) through combination of a plurality ofresults, intricate application control can be realized according to aplurality of methods.

In the above-described embodiment, the two methods of determining anincrease or decrease of the electrode pull-up distance by using the riseof the minimum point and the distribution density variation rate of theno-load time are stored in the knowledge memory section 42. However, itgoes without saying that more intricate and delicate application controlcan be achieved by determining machining conditions according to amethod in which the knowledge memory section 42 stores more than twomethods of determining machining conditions such as the pulse width,pulse interval and peak of a pulse current and an electrode pull-upperiod by using sounds generated during machining, vibration of themachining electrode, formation of bubbles in the machining solution,etc.

In the above-described embodiment, the results provided by the inferencesection 43 are combined according to equation 1; however, it goeswithout saying that the combination may be achieved by various methodsof using weighted mean, addition, maximum value, minimum value, etc.

In the above-described embodiment, the methods are stored in theknowledge memory section in a relatively free form as shown in FIG. 7.However, they may be stored in a form that "if . . . , then . . . ". Forinstance, method 2 stored in this form is as shown in FIG. 9. If method1 is expressed in the form that "if . . . , then . . . ", then thefollowing merits can be obtained: the storage is unified in form, andthe method can be stored in the knowledge memory section with ease, andthe processing operation of the inference section is simplified.

In the case of method 2a shown in FIG. 9, a quantitative value as in "if. . . is 0.8 or less" is indicated; however, the machining know how ofthe operator is often expressed using qualitative words such as "large"and "small". The method can be stored according to a rule using thefuzzy set theory which permits such qualitative expression. The methodsshown in FIG. 9 may be stored according to the fuzzy set theory as shownin FIG. 10.

In this case, in order to employ qualitative words such as "large" and"small", membership functions as shown in FIG. 11 are used.

For instance, in method 2A in FIG. 10, the following sentence isprovided: "if the distribution density variation rate of the no-loadtime is small". The fuzzy set for the word "small" of the sentence canbe expressed by the membership function corresponding to "small" in FIG.11, a diagram indicating the distribution density variation rate of theno-load time. For instance, if the variation rate is 0.7, thecorresponding membership function is 1, and if the variation rate is0.9, then the corresponding membership function is 1/3. In thisconnection, the membership function "1" means that it belongs completelyto the set, and the membership function "0" means that it does notbelong to the set at all.

In the case where, as in FIG. 10, a method is stored according to a rulebased on the fuzzy set theory, machining conditions are determined byfuzzy composition (or fuzzy inference). A variety of methods have beenproposed for fuzzy composition. One of the methods is as follows:

It is assumed that a rule has been expressed as follows:

Rule i: if x_(i) is A_(i) and y_(i) is B_(i), then set u to C_(i).

where x_(i) and y_(i) are the machining statuses or machining conditionssuch as the rise of the minimum point stored in the status memorysection 41, u is the machining condition applied to the electrodeposition control section 21 or the machining electric power source 22,A_(i), B_(i) and C_(i) are the fuzzy sets of "large", "small", etc., andthe suffix letter "i" means the i-th rule.

If the membership functions for A_(i), B_(i) and C_(i) are representedby f_(Ai), f_(Bi) and f_(Ci), respectively, then the aimed machiningcondition u_(t) can be obtained from the following equations (2) through(4):

    f.sub.ci (u)=f.sub.ci (u)*{f.sub.Ai (x.sub.i)  f.sub.Bi (y.sub.i)}(2)

    f.sub.c (u)= f.sub.ci (u)                                  (3)

    u.sub.t ={ f.sub.C (u) u du}/{ f.sub.C (u) bu              (4)

where and are the operators having a minimum value and a maximum value,and * is the multiplication or α-cut operator.

The results based on the plurality of rules are calculated according toequation (2), and are combined according to equations (3) and (4) toobtain the machining condition u_(t). Thus, intricate applicationcontrol based on a plurality of methods can be realized with ease.

In the above-described embodiment, the machining unit is the electricdischarge machine. However, it goes without saying that, for a laserbeam machine, beam machine, electro-chemical machine, NC lather, NCgrinding machine, etc. in which application control can be realized byadjusting machining conditions according to machining statuses,intricate application control can be readily realized by determiningmachining conditions with the results provided by the plurality ofmethods combined in the above-described manner. For instance, in a laserbeam machine, an application control device for determining the outputof a light source can be realized by combination of the results providedby a method of adjusting the output of a light source to prevent thewear at corners and by a method of adjusting the output of a lightsource according to the thickness of a plate.

As was described above, in the invention, the methods are stored in theknowledge memory section 42 independently of the inference section 43.Therefore, the methods can be readily modified merely adding or changingdata in the knowledge memory section. A procedure of executing a methodor a procedure of combining a plurality of methods is as indicated inFIG. 7 or the fuzzy inference (in the inference section 43) describedwith equations (2) through (4), which is unnecessary to change.

Let us consider the case where, for instance, a method of determiningthe electrode pull-up distance according to the vibration of theelectrode is added as method 3. In the case of "independent storage",all that is necessary to additionally store the method in the knowledgememory section 42. On the other hand, in the case of "dependentstorage", it is necessary to change the contents of the knowledge memorysection including the program in the application control section 31 withthe execution of the method, combination of the method with othermethods, and determination of the electrode pull-up distance taken intoaccount.

Now, a second embodiment of the invention will be described with theaccompanying drawings.

In the second embodiment, a method of determining a change of theelectrode pull-up distance as shown in FIG. 1 is stored in the knowledgememory section 42. In the cases of rules 1a, 1b and 1c, an increase ofthe electrode pull-up distance is determined according to the rise ofthe minimum point similarly as in the prior art. In the prior art, theincrease or decrease is determined by using the threshold value. On theother hand, in the invention, the method is stored in the knowledgememory section 42 by means of software independently of the inferencesection 43, and therefore an intricate method can be stored therein.Rules 2a, 2b and 2c indicate a method of controlling (increasing ordecreasing) the electrode pull-up distance according to the distributiondensity variation rate of the period of time which elapses from the timeinstant that a pulse voltage is applied across the discharge gap betweenthe electrode and the workpiece until electric discharge takes place(hereinafter referred to as "no-load time", when applicable). The methodcan be stored in the knowledge memory section 42 by using hardware suchas operational amplifiers and switches instead of software.

The storage will be described with reference to the flow chart of FIG.8. First, the inference section 43 reads rules 1a through 1c from theknowledge memory section 42, to obtain an increase or decrease Z₁ of theelectrode pull-up distance according to rules 1a through 1c in responseto the degree of rise of the minimum point stored in the status memorysection (Steps S31 through S34). Similarly, an increase or decrease Z₂of the electrode pull-up distance is obtained according to rules 2athrough 2c and the distribution density variation rate of the no-loadtime (Steps S35, and S32 through S34). Next, by combining the resultsprovided by the method, an increase or decrease Z_(t) is determined, andit is applied to the electrode position control section 21 and themachining electric power source 22 (Steps S36 and S37). Similarly as inthe above-described equation (1), the results may be averaged.

In the employment of rules 2a through 2b, it is necessary to obtain thedistribution density variation rate of the no-load time. It can beobtained as follows: In the detection value processing section 23, theno-load time is measured for a predetermined interval. By using theno-load time thus measured, a distribution density variation rate iscalculated according to equation (5) shown in FIG. 7, and stored in thestatus memory section 41. In the case of rules 1a through 1c, it isnecessary to obtain the degree of rise of the minimum point. In thiscase, it is obtained in the detection value processing section 23, andstored in the status memory section 41.

Thus, by obtaining a machining condition (increase or decrease of theelectrode pull-up distance) through combination of a plurality ofresults, intricate application control can be realized according to aplurality of methods.

In the above-described second embodiment, the method of determining anincrease or decrease of the electrode pull-up distance by using the riseof the minimum point and the distribution density variation rate of theno-load time is stored in the knowledge memory section 42. However, itgoes without saying that more intricate and delicate application controlcan be achieved by determining machining conditions according to amethod in which the knowledge memory section 42 stores a method ofdetermining machining conditions such as the pulse width, pulse intervaland peak of a pulse current and an electrode pull-up period by usingsounds generated during machining, vibration of the machining electrode,formation of bubbles in the machining solution, etc.

In the above-described second embodiment, the results provided by theinference section 43 are combined according to equation 1; however, itgoes without saying that the combination may be achieved by variousmethods of using weighted mean, addition, maximum value, minimum value,etc.

Furthermore, communication means or the like may be used to allow partor all of the data of the rules stored in the knowledge memory section42 to be used by the machining unit application control apparatus andothers machining unit application control apparatuses in common. Hence,in a factory or the like having a plurality of machining units which aresimilar in function, common machining know-how techniques can becollectively controlled, and the machining know how peculiar to eachmachining unit can be controlled by its own machining unit applicationcontrol apparatus.

Furthermore, if part or all of the data of the rules stored in theknowledge memory section 42 are transferred into a magnetic disk so thatthey are returned to the section when necessary, then, with one and thesame machining unit, machining operations based on different machiningknow how techniques can be realized with ease. The same effects can beobtained by using an optical disk, IC cartridge, magnetic bubble memory,magnetic tape, or the like instead of the magnetic disk.

In the above-described second embodiment, the machining unit is theelectric discharge machine. However, it goes without saying that, for alaser beam machine, beam machine, electrochemical machine, NC lather, NCgrinding machine, etc. in which application control can be realized byadjusting machining conditions according to machining status, intricateapplication control can be readily realized according to a method inwhich the machining know how techniques of the operator are storedaccording to the rules, and the results thereof are combined todetermine machining conditions. For instance, in a laser beam machine,an application control device for determining the output of a lightsource can be realized by combination of the results provided by amethod of adjusting the output of a light source to prevent the wear atcorners and by a method of adjusting the output of a light sourceaccording to the thickness of a plate.

The rule shown in FIG. 7 is made up of rules 1a through 1c and rules 2athrough 2c; however, an application control apparatus may be realized,for instance, by writing one rule which is a consolidation of rules 1athrough 1b.

In the above-described second embodiment, data are written in the formof rules in the knowledge memory section 42; that is, the writing formis unified, and therefore it is possible to rewrite essential parts onlyin such a manner that only a front condition part or rear condition partis written. Therefore, in this case, addition and modification of themethods can be achieved more readily than in the case of FIG. 7. In thecase of FIG. 2, modification of the method will require much timebecause it is necessary to understand all the sentence of the method.

Now, a third embodiment of the invention will be described withreference to FIG. 13.

In FIG. 13, reference numerals 51 through 63 designates the same itemsas those in the figures showing the prior art. Further in FIG. 13,reference character 42a designates a knowledge memory section; 68, amethod read out of the knowledge memory section 42a; 69, machiningstatus data required at least for the method stored in the knowledgememory section 42a; 70 a status detecting unit for detecting themachining status data; 71, a detection value provided by the statusdetecting unit 70; 72, a status memory section for storing at least oneof the current and past detection values 71; 73, status data necessaryfor the above-described method 68 read out of the status memory section41a; 43a, an inference section for collectively determining a mostsuitable jumping operation and most applicable change according to themethod 68 stored in the knowledge memory section 42a and the status data73 stored in the status memory section 41a; and 75, an instruction valueapplied to a jump controlling unit 60 by the inference section 43a.

Similarly as in the case of FIGS. 1 and 4, in FIG. 6 the mechanical partof the machining unit is represented by the mechanical elements 1through 7, while in FIG. 13 an input, inter-electrode distance, and anoutput, machining state data are expressed as objects to be controlled.Hence, it is rather difficult to directly compare FIGS. 6 and 13 witheach other. However, the following components correspond relatively oneanother in FIGS. 6 and 13:

The electrode position control section 21 in FIG. 6 corresponds to thecombination of the electrode control system 53, the jump controllingunit 60 and the switching unit 62 in FIG. 13.

The state recognizing section 23 corresponds to the combination of thestate detecting unit 55 and the status detecting unit 70.

The status memory section 41 corresponds to the combination of thestatus memory section 41a and the instruction value setting unit 57.

The knowledge memory section 42 corresponds to the knowledge memorysection 42a.

The inference section 43 corresponds to the knowledge section 43a.

A method of forming the instruction value 75 most suitable for thejumping operation of the machine in the embodiment shown in FIG. 13 willbe described. FIG. 14 is an explanatory diagram showing one example of amethod of effectively causing the machining electrode to jump. It isimpossible for a conventional electric discharge machining controldevice to write such a method effectively and readily. In the invention,a fuzzy set as shown in FIG. 15 is utilized to write methods as shown inFIG. 14 in the knowledge memory section 42a according to a ruleconsisting of a front condition part "IF" and a rear condition part"THEN". More specifically, qualitative fuzzy expressions "machiningcurrent is large", "clearance is small", "machining depth is large","jumping distance is short", etc. included in the methods of FIG. 14 areexpressed as membership functions. For instance, in the case of afeature "machining current is large" in method 1 of FIG. 14, if themachining current is 15 A or less, the feature does not meet thecondition, and therefore the membership function is set to zero; if themachining current is 35 A or higher, then the feature meets thecondition completely, and the membership function is set to "1"; and ifthe machining current is between 15 A and 35 A, then the feature meetsthe condition between "0" and "1", and the membership function is set to"0-1". Similarly, the other qualitative fuzzy expressions can beappropriately and readily written with membership functions.

On the other hand, with the aid of the state detecting unit 70, thestatus memory section 41a detects and stores machining statusesnecessary for the methods stored in the knowledge memory section 42a.Furthermore, the status memory section 41a receives and stores knowndata such as machining current.

In the case of FIG. 14, necessary machining statuses are machiningcurrent, clearance and machining depth. The machining current is a knownvalue because the operator can set it as one of the machiningconditions.

The clearance is determined mainly from an inter-electrode servo voltage(an instruction value from the machining gap control system), aninter-electrode voltage and a set machining current, and is known asmachining condition data.

The machining depth is provided, as the positional difference between amachining start position and a current position, by the electrodeposition detecting unit.

The inference section 43a performs a fuzzy inference according to aprocedure shown in FIG. 16 according to the methods stored in theknowledge memory section 42a and the statuses stored in the statusmemory section 41a, to determine an instruction value 75 for the mostsuitable jumping operation of the machining electrode. In FIG. 16,reference characters 73a, 73b and 73c designate the known data anddetection values of the machining current, clearance and machining depthstored in the status memory section 41a, respectively. With the fuzzyinference, in each method it is detected to what extent these statusdata 73 satisfy the qualitative expressions in the front condition partdescribed with the membership functions, and the upper limit of themembership function of the rear condition part is cut to the value ofthe membership function which is minimum in the degree of satisfactionin the front condition. And the resultant membership functions arecombined so as to have the largest of the function values of the givenmembership functions at all times, and the area gravity center positionC.G. of the composite of the membership function is obtained. This isthe instruction value 75 for the most suitable jumping operation of themachining electrode.

In FIG. 16, in each method, the front condition part describes threemachining status, while the rear condition part one jumping operationdata; however, the invention is not limited thereby or thereby. It goeswithout saying that, in the case where the number of methods isincreased, an instruction value for the best jumping operation of themachining electrode can be obtained similarly. For the third embodimentof the invention, changing the jumping operation suitably according tothe degree of instability of the discharging machining state has notbeen described; however, the changing of the jumping operation can berealized similarly as in the above-described case.

In the above-described third embodiment of the invention, the fuzzy setis utilized for the knowledge memory section and the fuzzy inference isperformed by the inference section. However, it goes without saying thata knowledge expression and inference method utilized for other generalexpert systems can be utilized in the invention with the same effects asin the third embodiment.

Now, a fourth embodiment of the invention will be described. FIG. 17 isa block diagram showing the arrangement of the fourth embodiment, amachining unit application control apparatus. In FIG. 17, referencenumeral 10 designates an operator; 20, a machining unit; 42, a knowledgememory section in which operator's machining methods are stored; 23, astate recognizing section for recognizing machining states; 41, a statusmemory section for storing machining conditions set for the machiningunit 20 and machining states recognized by the state recognizing section23; 43, an inference section for inferring the operation of themachining unit 20 from the machining statuses stored in the statusmemory section 41 using the machining methods stored in the knowledgememory section; and 87, a first arrangement group including theabove-described sections 23, 41, 42 and 43. Further in FIG. 17,reference numeral 88 designates a time-series data recording section forrecording time series data of the machining states recognized by thestate recognizing section 23, the machining conditions set for themachining unit 20 and the operations performed by the operator 10; 89, aknowledge renewing section for extracting a machining method from thecontents stored in the time-series data recording section 88 andcombining it with the output of the inference section 43 to form amachining a method or correct it, thereby to renew the contents of theknowledge memory section 42; and 90, a second arrangement groupconsisting of the above-described sections 88 and 89.

The operation of the apparatus thus organized will be described. Inmachining an Al material with a machining unit 20, a method foradjusting a machining condition A as shown in the part (a) of FIG. 18,which is practiced by the operator 10, is stored in the knowledge memorysection 42 as shown in the part (b) of FIG. 18.

As shown in a flow chart of FIG. 20, upon start of a machiningoperation, it is determined whether or not the machining operation hasbeen ended (Step S41), and the state recognizing section processes theoutput signal of a sensor installed on the machining unit 20 to detectthe machining speed and the machining sound magnitude, thereby torecognize the machining state (Step S42). The machining speed and themachining sound magnitude together with the machining conditions arestored, as a machining status, in the status memory section 41 (StepS43). The inference section 43 infers a machining condition changingoperation from the machining status using a method stored in theknowledge memory section 42 (Step S44). For instance, in the case where,with respect to predetermined reference values, machining sound 3/2,machining speed 1 and condition B4 are obtained, K₁ =-2/3, K₂ =-1 and K₃=4 according to the table shown in the part (b) of FIG. 18, andtherefore ##EQU2## Thus, the machining condition A is set to [11/6]. Theabove-described operation will become more apparent from the part (c) ofFIG. 18, being indicated by three-dimensional functions, machiningspeed, machining sound and operating data.

That is, the machining unit application control apparatus controls themachining unit 20 according to the operator's machining method using thefirst arrangement group, thus repeatedly carrying out Steps S41 throughS44 until the machining operation is accomplished.

Now, an operation of correcting the operator's machining method storedin the knowledge memory section 42 will be described.

As shown in a flow chart of FIG. 21, during machining, part or all ofthe machining condition is changed (Step S51), and the time-series datarecording section 88 is operated to record time-series data of the setmachining conditions, machining states, and machining condition changingoperation performed by the operator (Step S52). When the machiningconditions are changed by the operator, the output of the inferencesection 43 is also recorded (Step S52). Thereafter, after the machiningoperation, the knowledge renewing section 89 corrects the machiningmethod stored in the knowledge memory section 42 if the machiningcondition selected by the operator differs from that which is inferredby the inference section 43 (Step S53).

This will be concretely described with reference to FIG. 19. It isassumed that as a result of the machining of an Al material whosecondition B is 3, the contents of the time-series data recording section88 is as shown in the part (a) of FIG. 19. In this case, since theoutput (inference value) of the inference section 43 is different fromthe operation of the operator, the machining method is amended asfollows: That is, the amendment is carried out according to the methodof least squares. In the case where the operation is represented by y,the machining speed u₁, and the machining sound magnitude u₂ themachining method can be expressed as follows:

    y=K.sub.1 u.sub.1 +K.sub.2 u.sub.2 +K.sub.3                (1)

Owing to the recording of the operation of the operator,

    (y.sub.i, u.sub.1i m u.sub.2i) (i=1, 2, . . . and 6)       (2)

With

    e.sub.i =K.sub.1 u.sub.1 +K.sub.2 u.sub.2 +K.sub.3 -y.sub.i(3)

K₁, K₂ and K₃ are obtained which minimizes the following equation (4)and are stored in the knowledge memory section 42: ##EQU3##

By partial differentiation of equation (4) with respect to K₁, K₂ andK₃, ##EQU4## From equations (5), (6) and (7),

    K.sub.1 =-1, K.sub.2 =-3/2, and K.sub.3 =7                 (8)

The contents of the knowledge memory section 42 are renewed usingequation (8). That is, the contents of the knowledge memory section 42are changed from those shown in the part (b) of FIG. 18 into those shownin the part (b) of FIG. 19. Thus, the machining method of the operatorhas been amended.

Now, an operation of collecting the machining methods of the operatorand adding them to the contents of the knowledge memory section will bedescribed with reference to the case where machining methods concerningthe machining of a Cu material are collected. Similarly as in theabove-described case of correcting an Al material machining method, thetime-series data recording section 88 is operated to record time-seriesdata of set machining conditions, machining states, operations done bythe operator, and machining conditions inferred by the inference section43, and the knowledge memory section 89 operates K₁, K₂ and K₃ inequation (1) according to the method of least squares.

The machining methods thus collected are stored in the knowledge memorysection 42. This operation is greatly different from the above-describedoperation of correcting the machining method as follows: In the latteroperation, the values stored are renewed, whereas in the latteroperation, a region for storage is reserved, and the machining methodsare stored in the region thus reserved. The machining methods of theoperator are collected in the above-described manner. Thus, theoperation of adding the machining methods to the contents of theknowledge memory section 42 has been accomplished.

In the above-described embodiment, only one operator is employed. Whenmore than one operators are used, more than one knowledge memorysections 42 may be provided so that the operators are assigned to thosesections, respectively; or one knowledge memory section 42 may bedivided into more than one part so that the operators are assigned tothose parts, respectively. In this case, the operator can store his ownmachining method in his own knowledge memory section 42.

In the case where operators' data are provided separately according tothe operators, the names of the operators or personal data correspondingthereto are stored in the knowledge memory section 41 by using akeyboard, IC card, magnetic card, magnetic disk or optical disk.

In the invention, the machining unit may be an electric dischargemachine, laser beam machine, beam machine, electrochemical machine, NCmachine, or NC machine tool. In each machining unit, the same effects asthose in the above-described fourth embodiment can be obtained with thesignals changing with machining state applied to the state recognizingsection 23.

FIGS. 22, 23 and 24 are block diagrams showing fifth, sixth and seventhembodiments of the invention, machining unit application controlapparatuses, respectively.

In the fifth embodiment shown in FIG. 22, an example indicating section91 is provided in the second arrangement group. In the embodiment, theexample indicating section 9 provides a machining example, and how tohandle the machining example by the operator is recorded in thetime-series data recording section 88. More specifically, in the casewhere the operator collects or correct machining methods, an examplemachining operation is carried out by using the first arrangement group87 and the second arrangement 90; that is, the operator is allowed tochange part or all of the machining conditions without using the outputof the inference section 43, so that the machining method stored in theknowledge memory section 42 are renewed by the knowledge renewingsection 89. Hence, the machining methods of the operators can bepositively collected.

Part or all of the machining method to be stored in the knowledge memorysection 42 may be made up of a rule (IF--, THEN--) which consists of afront condition part including conditions to be determined and a rearcondition part including the contents which are to be carried out whenthe conditions are satisfied and when not satisfied.

In addition part or all of the rule may be a fuzzy rule which isexpressed on the fuzzy set theory which handles fuzzy expressions suchas for instance "amplitude is large" and "move down a little". In thiscase, membership functions for a fuzzy set employed for expression ofthe front and rear condition parts, and the relationships between themembership functions are stored in the knowledge memory section 42, andfuzzy composition is carried out by the inference section 43 to combinea plurality of results from the machining states and machiningconditions stored in the status memory section 41 and from the fuzzyrule concerning them stored in the knowledge memory section 42, wherebymachining conditions for desirable machining states are obtained.

In this case, the apparatus may be so modified that the machiningmethods in the knowledge memory section 42 are corrected by changing themembership functions.

In the sixth embodiment shown in FIG. 23, a rotary knob 92, which theoperator can freely operate, is provided in the second arrangement groupso that analog data are inputted into the time-series data recordingsection. In the sixth embodiment, the quantity the operator feels can beinputted. Therefore, when the operator employs a method that "machiningconditions are changed when machining sound is large, the degree towhich he feels a machining sound large can also be recorded. Thus, themachining methods can be more positively collected.

In the above-described sixth embodiment, the rotary knob 92 is employedto input analog data; however, it may be replaced with a slide knob orjoy stick switch. The positions of the knob or switch are detected by apotentiometer or rotary encoder (not shown) and applied through an A/D(analog-to-digital) encoder or up-down counter (not shown) to thetime-series data recording section 88.

The above-described input device may have a plurality of push buttons,so that at least one of the following items is inputted by depressing atleast one push button:

(a) The start of a machining condition changing operation which is to becarried out

(b) The completion of a machining condition changing operation, whichhas been achieved by the operator

(c) The self-evaluation of a machining condition changing operationwhich has been performed by the operator

(d) The cancellation of a machining condition changing operation whichhas been achieved by the operator

(e) The reason why the operator has performed a machining conditionchanging operation

In the seventh embodiment shown in FIG. 24, a CRT display unit 93 isprovided. In the embodiment, the machining methods stored in theknowledge memory section 42 can be displayed, so that it can bedetermined whether or not collection or correction of the machiningmethods has been positively performed. Instead of the CRT display unit93, a liquid crystal panel or plasma display may be employed. With thedisplay means, at least one of the following items (a) through (g) isdisplayed:

(a) Machining conditions

(b) Outputs of the knowledge renewing section 89

(c) Renewal of the methods in the knowledge memory section 42

(d) Status of inference by the inference section 42

(e) Any one or all of the methods stored in the knowledge memory section42

(f) Contents stored in the time-series data memory section 88

(g) Operator's name, or personal data corresponding thereto

When the example indicating section 81 outputs an example, the provisionof the example is indicated on the display means such as a CRT displayunit so as to allow the operator to confirm the operating status of themachining unit.

Similarly as in the second embodiment, the knowledge memory section 42may be so designed that it is removable. In this case, one and the sameknowledge memory section 42 can be used in common by a plurality ofmachining units equal in type, and therefore these machining units canperform machining operations according to the same machining method. Inthis case, the memory medium may be a magnetic disk, optical disk, ICcard, IC cartridge, magnetic bubble memory, and magnetic tape.

In the above-described embodiment, with respect to the machiningcondition and machining status used for the inference of the inferencesection, simple application control can be achieved even if themachining conditions are not sufficient; that is, the simple applicationcontrol can be performed only with machining conditions such asmachining speed and machining sound.

The term "machining state" as used herein is intended to mean datarepresenting a machining state which is provided by a detector.

The term "machining condition" as used herein is intended to means datasuch as set values and target values which affect machining operations.

The term "machining status" or "status" as used herein is intended meanboth of the machining state and machining condition.

As was described above, in the prior art, the machining operation isperformed according to the simple method, and in order to realize anintricate method, it is necessary to describe a considerably complicatedmethod. On the other hand, according to the first aspect of thisinvention, by writing methods such as machining know how techniques inthe knowledge memory section independently of the inference section,addition and modification of the methods can be readily achieved. Inaddition, in the invention, the operating data provided by the inferencemechanism according to a plurality of methods are combined, so that anintricate application control can be readily realized with a variety offactors taken into account.

According to the second aspect of the invention, methods such asmachining know how techniques are independently written in the knowledgememory section according to a predetermined rule, as a result of whichaddition and modification of the methods can be achieved more readily,and use of the knowledge memory section in common makes it possible tocontrol the machining know how techniques with ease and to use them incommon.

According to the third aspect of the invention, a method effective injumping the machining electrode is stored in the knowledge memorysection, machining status data necessary at least for the method isstored in the status memory section, and the inference sectiondetermines a jumping instruction value from the method stored in theknowledge memory section and the machining status data stored in thestatus memory section. Hence, the skilled operator's methods of jumpingthe machining electrode can be stored with ease, and according to thosemethods suitable execution and change of the jumping operation can beautomatically achieved.

According to the fourth aspect of the invention, the application controlapparatus is so designed that operator's machining methods can beutilized for automatic machining operations, which contributes to laborsaving. Furthermore, in the application control apparatus, for the samereason the operators' machining methods can be collected or correctedwith ease.

Another embodiment of the invention will be described with reference toFIG. 25. In FIG. 25, reference numerals 1 through 33 designate the samecomponents or functions as those in FIG. 5 (the conventional apparatus);140, an automatic positioning control unit; 141, a first memory sectionfor storing a positioning procedure, and a method of determining whetheror not the result of an automatic positioning operation is acceptable;143, a second memory section for storing the status of the electrode 1and the workpiece 2 which are to be position-controlled, and the statusof an automatic positioning operation; and 142, a logic section.

The operation of the application control apparatus thus organized willbe described. A plurality of methods have been stored in the firstmemory section which is adapted to store a positioning procedure and amethod of determining whether or not the result of an automatic positionoperation is acceptable. More specifically, a plurality of method ofdetermining an automatic positioning speed and an automatic positioningfrequency as shown in the parts (a) and (b) of FIG. 26 are stored in thefirst memory section 141, and in addition a plurality of methods ofdetermining an automatic positioning operation completion position fromthe result of an automatic positioning operation as shown in FIG. 29 arestored in the first memory section 141. In the part (a) of FIG. 26,method 1 is to determine an automatic positioning speed according to anelectrode diameter. More specifically, the automatic postioning speed isdetermined in several steps in such a manner that the automaticpositioning speed is extremely high for an electrode small in diameter,and it is extremely low for an electrode large in diameter. In method 2,an automatic positioning speed is determined according to a contactarea. That is, the automatic positioning speed is determined in severalsteps in such a manner that it is extremely low in the case where thecontact area is small, and it is extremely high in the case where thecontact area is large. In method 3, an automatic positioning speed isdetermined according to the distance of movement in the automaticpositioning operation; i.e., an approaching distance. More specifically,the automatic positioning speed is determined in several steps in such amanner that it is extremely high in the case where the approachingdistance is long, and the automatic positioning operation is startedwith the electrode far from the workpiece, and it is extremely low inthe case where the approaching distance is short, and the automaticpositioning operation is started with the electrode near to theworkpiece.

In the part (b) of FIG. 26, method 1 is to determine an automaticpositioning frequency according to a contact area. More specifically,the automatic positioning frequency is determined in several steps insuch a manner that the automatic positioning operation is performed onlyonce for the electrode which is small in contact area, or has a sharptip, and the automatic position operation is carried out several timesfor the electrode which is large in contact area. In method 2, anautomatic positioning frequency is determined according to a contactsurface roughness. More specifically, the automatic positioningoperation is carried out only once for the electrode whose contactsurface is high in surface roughness as in a mirror, and it is carriedout several times for the electrode whose contact surface is low insurface roughness as in an electrode used for discharge machiningoperations. In method 3, an automatic positioning frequency isdetermining according to an automatic positioning speed. That is, theautomatic positioning operation is carried out several times in the casewhere the automatic positioning speed is high, and it is carried outonly once in the case where the automatic position speed is low. Theabove-described methods of determining an automatic positioning speedsand automatic positioning frequencies are operator's know howtechniques, which are stored in the first memory section 141.

FIG. 27 is a flow chart showing a method of determining most suitableautomatic positioning speeds and automatic positioning frequenciesaccording to the methods stored in the first memory section 141 and tothe status of an electrode and a workpiece to be automaticallypositioned which is stored in the second memory section 143 with the aidof the logic section 142. First, the logic section 142 reads method 1from the first memory section 141 to determine an automatic positioningspeed F₁ according to the electrode diameter area stored in the secondmemory section 143. It reads method 2 to determine an automaticpositioning speed F₂ according to the contact area stored in the secondmemory section 143. Similarly, it determines an automatic positioningspeed F₃. The three automatic positioning speeds thus determined arecombined to obtain a final automatic positioning speed Ft. Thecomposition of the speed Ft can be achieved by averaging those resultsfor instance as follows: ##EQU5## where Nj is the total number ofmethods for an object j.

Thereafter, method 1 for another object is read, so that an automaticpositioning frequency T₁ is determined according to the contact areastored in the second memory section 143. Next, method 2 is read, so thatan automatic positioning frequency T₂ is determined according to thecontact surface roughness stored in the second memory section 143.Similarly, an automatic positioning frequency T₃ is obtained accordingto method 3 read out. The three automatic positioning frequencies thusdetermined are combined to obtained a final automatic positioningfrequency Tt. The composition of the frequency Tt can be achieved byaveraging those result similarly as in the above-described equation (1):##EQU6## where Nj is the total number of methods for an object j.

Under this condition, the status of the electrode and the workpiece isread from the second memory section 143. The electrode diameter, thecontact area of the electrode and the workpiece, the distance betweenthe electrode and the workpiece at the start of an automatic positioningoperation (i.e., the approaching distance), the surface roughness of theelectrode and the workpiece, and the automatic positioning speeddetermined according to the above-described equation (1) are stored inthe second memory section 143. Those data have been set in advance.

An automatic positioning operation is carried out with the automaticpositioning speed and frequency thus obtained, as a result of which anautomatic positioning operation completion position is obtained. Morespecifically, the position of completion of the automatic positioningoperation is obtained by using a plurality of methods which are storedin the first memory section 141 as shown in FIG. 29. In FIG. 29, method1 is used to determine a degree of confidence in the completion positionaccording to an automatic positioning average dispersion value. Inmethod 2, a degree of confidence in the completion position isdetermined according to an automatic positioning maximum dispersionwidth. In method 3, a degree of confidence in the completion position isdetermined according to a voltage at the completion of the automaticpositioning operation. That is, when the electrode is in contact withthe workpiece, the degree of confidence that the position of theelectrode is the automatic positioning operation completion position isextremely high; whereas when the electrode is spaced apart from theworkpiece, and the voltage is developed across the inter-electrode, thedegree of confidence is extremely low. The logic section 142 determinesa degree of confidence in the automatic positioning operation completionposition from the methods stored in the first memory section 142 and theresults of automatic positioning operations stored in the second memorysection 143. The determination is carried out according to a methodwhich is equivalent to that which is shown in the flow chart of FIG. 27.According to the degree of confidence thus determined, the automaticpositioning operation completion position is determined according to aflow chart of FIG. 30.

In the above-described embodiment, the first memory section 141 storesthe method of determining an automatic positioning speed by using threemethod of obtaining automatic positioning speeds from three factors,electrode diameter, contact area and approaching distance, respectively,and the method of determining an automatic positioning frequency byusing three methods of obtaining automatic positioning frequenciesaccording to three factors, contact area, contact surface roughness andautomatic positioning speed, respectively. However, the detection may becarried out by using a degree of environmental contamination in air oroil, or the electrical conductivity of the electrode or workpiece.Furthermore, a method of determining the voltage from these factorswhich is applied during the automatic positioning operation.

In the above-described embodiment, the logic section 142 employsequation (1) for combination of the results obtained according to themethods; however, the composition may be achieved according to a varietyof methods using weighted mean, maximum value, minimum value, etc.

The first memory section, the second memory section, and the logicsection may be formed according to the algorithm on inference which iswritten according to a fuzzy rule. In addition, the first memorysection, the second memory section, and the logic section may beprovided in the numerical control unit.

Furthermore, in the above-described embodiment, the electrode andworkpiece positioning detecting means operates on electrical contact;however, physical contact type detecting means or non-contact typedetecting means may be employed.

As is apparent from the above description, according to the invention,the methods such as positioning know how techniques, which can bepracticed by a person, but are difficult to fix because the controlmodel is intricate, are stored in the first memory section. Hence,addition and modification of the methods can be readily achieved.Furthermore, according to the invention, the logic section 142 operatesto combine the results provided according to a plurality of methods, toprovide the final result with a variety of factors taken into account.Thus, the automatic positioning operation can be achieved with higherstability and with higher accuracy.

Another embodiment of the invention will be described. FIG. 31 is ablock diagram showing the embodiment, a machining operation completiondetermining unit. In FIG. 31, reference numeral 1 designates anelectrode; 2, a workpiece to be machined; 3, a machining vessel; 4, amachining solution; 5, a Z-aixs for moving the electrode 1 in such amanner that the latter 1 is pushed into the workpiece; 6, a Z-axis drivemotor; 7, a detector for detecting the speed and position of the Z-axis5; 8 and 9, an X-axis and a Y-axis for moving the electrode 1 and theworkpiece relative to each other in directions perpendicular to thedirection of the Z-axis 5, respectively; 10, an X-axis drive motor; 11,a Y-axis drive motor; 12, a detector for detecting the speed andposition of the X-axis 8; 13, a detector for detecting the speed andposition of the Y-axis 9; 14, a machining solution pressure meter; 21,an electrode position control section; 22, a machining electric powersource; 23, a detection value processing section; and 220, the machiningoperation completion determining unit. The unit 220 comprises: a firstmemory section 221 which stores a plurality of methods concerningdetection and analysis of machining environmental factors such asmachining solution jet pressure, machining area, machining depth andoscillation radius; a second memory section which stores present and/orpast machining state and machining environment; and a logic section 223for combining a plurality of results provided according to the machiningstate and machining environment stored in the second memory section 222and the plurality of methods stored in the first memory section 221, toobtain a correct machining operation completion determining parameter,thereby to perform a machining operation completion determination.Further in FIG. 31, reference numeral 224 designates input means such asa keyboard.

The operation of the machining operation completion determining unitthus constructed will be described. The parts (a), (b) and (c) of FIG.32 show the methods concerning detection and analysis of machiningenvironmental factors which are stored in the first memory section 221;more specifically, a plurality of methods of determining the range ofdifference Ve between an electric discharge machining voltage and areference voltage which is one of the machining operation completiondetermining parameters.

In method 1 shown in the part (a) of FIG. 32, the data Ve is determinedaccording to machining solution jet pressure. When the machiningsolution jet pressure is 0; i.e., no machining solution jet is provided,Ve is OV. That is, it is regarded that, when the machining operation iscarried out normally, the range of difference Ve, the machiningoperation completion determining parameter, is satisfied. When themachining solution jet pressure is 0.5 kg/cm², Ve is 6 V. That is, it isregarded that, when the completely open state is obtained, the machiningoperation completion determining parameter Ve is satisfied. This isbased on the fact that the inter-electrode gap between the electrode andthe workpiece is large when no machining solution jet is provided,whereas it is small when the machining solution jet is provided.

In method 2 shown in the part (b) of FIG. 32, the data Ve is determinedaccording to a machining area. Where a machining area is small, wastematerial such as sludge is distributed, and it is removed with highefficiency; and therefore it is regarded that, when the completely openstate is obtained, the machining operation completion determiningparameter is satisfied. On the other hand, when the machining area islarge, then the waste material is non-uniformly distributed, and it isdifficult to remove, and therefore the inter-electrode gap between theelectrode and the workpiece is large. Accordingly, in this case, it isregarded that, when Ve is 0; i.e., when the machining operation iscarried out normally, the machining operation completion determiningparameters is satisfied.

In method 3 shown in the part (c) of FIG. 32, the data Ve is determinedaccording to a machining depth. In the case where the machining depth issmall, waste material such as sludge can be removed with highefficiency, and therefore it is regarded that, when the completely openstate is obtained, the machining operation completion determiningparameters is satisfied. When, on the other hand, the machining depth islarge, then the waste material become difficult to remove, and theinter-electrode gap between the electrode and the workpiece becomeslarge; and therefore it is regarded that, when Ve is OV; i.e., when themachining operation is carried out normally, the machining operationcompletion determining parameters is satisfied.

The parts (a), (b) and (c) of FIG. 33 show methods of determining theduration time T within the range of difference Ve between a dischargemachining voltage and a reference voltage which is another one of themachining operation completion determining parameter.

In method 1 shown in the part (a) of FIG. 33, the time T is determinedaccording to a machining solution jet pressure. When no machiningsolution jet is applied, Ve is OV as was described before, and thereforeit is regarded that, when the machining operation is performed stablyfor one second, the duration time within Ve is satisfied. When, on theother hand, the machining solution jet is used, Ve is 6V, and thereforeit is useless to set the duration time to a value larger than required;that is, it is regarded that, when the machining operation is carriedout stably for a period of time which is long enough, the machiningoperation completion determining parameter T has been met.

In method 2 shown in the part (b) of FIG. 33, the time T is determinedaccording to a machining area. For instance, in the case where a smallhole is formed, the amount of machining is small, and accordingly thetime T may be short. On the other hand, as a machining area increases,the amount of machining is increased, and therefore T is set to onesecond in order to confirm that a machining operation is stable withinVe. However, when a machining area is extremely large, it is ratherdifficulty to remove the waste material such as sludge formed. Thisdifficulty may be eliminated by increasing T. However, increasing Tmakes it difficult to determine whether or not the machining operationhas been accomplished. Hence, in contrast, the time T is decreased.

In a method 3 shown in the part (c) of FIG. 33, T is determinedaccording to an oscillation radius. Where the oscillation radius issmall, the total circumference of oscillation can be determined with ashort duration time T; whereas where the oscillation radius is long, thetotal circumference of oscillation cannot be determined without a longduration time T.

FIG. 34 is a flow chart for a description of a method in which the logicsection 223 determines the range of difference Ve between dischargemachining voltage and reference voltage and the duration time T withinthe range of difference Ve, which are the machining operation completiondetermining parameters, according to the methods stored in the firstmemory section 223 and the machining environmental conditions such asmachining solution jet pressure, machining area, machining depth andoscillation radius which are stored in the second memory section 222.

First, with j=1 and i=1 in Steps 40 and 42, the logic section 223 readsobject 1; that is, method 1 concerning the range of difference Vebetween discharge machining voltage and reference voltage, which is onemachining operation completion determining parameter, from the firstmemory section 221 (Step 42). In Step 43, the logic section reads amachining environmental condition concerning method 1; i.e., themachining solution jet pressure, from the second memory section 222, andutilizes the machining solution jet pressure thus read to obtain a rangeof difference Vel between discharge machining voltage and referencevoltage according to method 1 (Step 44).

Next, in Step 45, the logic section reads method 2 concerning Ve, and,similarly as in the above-described case, utilizes the machining areastored in the second memory section 222 to obtain a range of differenceVe2 between discharge machining voltage and reference voltage accordingto method 2 (Step 44). Similarly, a range of difference Ve3 is obtainedaccording to method 3. In Step 46, it is determined whether or not allthe methods have been used for the object.

The results provided by the three methods are combined (Step 47) toobtain a range of difference Ve between discharge machining voltage andreference voltage is obtained (Step 48). The composition is performed,for instance, by averaging those results according to the followingequation (1): ##EQU7## where Nj is the total number of methods for anobject j.

Thereafter, the object is switched over to another one (Steps 49 and50). Method 1 concerning the new object; i.e., the duration time Twithin the range of difference Ve is read (Step 42), and the machiningsolution jet pressure stored in the second memory section 222 isutilized to obtain a duration time T1 within Ve according to method 1(Step 44). Similarly as in the above-described case, method 2 is read,and the machining area stored in the second memory section 222 isutilized to obtain a duration time T2 within Ve according to method 2.Similarly, a duration time T3 is obtained according to method 3. Theresults provided by the three methods are combined (Step 47) todetermined a duration time T within Ve (Step 48). This composition isperformed by averaging those results according to the following equation(2): ##EQU8## where Nj is the total number of methods for an object j.

The above-described machining solution jet pressure, machining area,machining depth, and oscillation radius are stored in the second memorysection 222 as follows: The machining solution jet pressure is stored asfollows: In FIG. 31, the machining solution pressure meter 14 appliesthe pressure of the machining solution 4 to the detection valueprocessing section 23, so that the machining solution pressure is storedin the second memory section. The machining area is stored as follows:That is, data inputted through the input means such as a keyboard by theoperator is stored, as the machining area, in the second memory section222. The machining depth is stored as follows: The output signal of thedetector 7 for the speed and position of the Z-axis 5 is applied to thedetection value processing section 23, where the amount of movement ofthe Z-axis with the machining electric power source 22 on; i.e., amachining depth is obtained. The machining depth thus obtained is storedin the second memory section 222. In the case of the oscillation radius,the output signals of the speed and position detectors 12 and 13provided respectively for the X-axis 8 and Y-axis 9 are applied to thedetection value processing section 23, where the maximum amounts ofdisplacement of the X-axis and Y-axis are obtained, and stored, as theoscillation radius, in the second memory section 222.

The range of difference Ve between discharge machining voltage andreference voltage and the duration time T within the range of differenceVe are utilized for determination of the completion of the machiningoperation. This determination is carried out by the logic section 223according to a flow chart of FIG. 35 as follows:

In Step 51, it is determined whether or not the electrode has reached adesired position in the direction in which it is pushed into theworkpiece. The term "desired position" as used herein is intended tomean the position which is obtained when the difference between theposition which is inputted through the input means 224 (FIG. 31) inadvance and stored in the second memory section 222 and the positionwhich the speed and position detector 7 applies as its output signal tothe second memory section 22 through the detection value processingsection 23 becomes zero. In Step 52, a timer for measuring a durationtime T is reset. In Step 53, the discharge machining voltage and thereference voltage are read. The discharge machining voltage is stored asfollows: That is, the inter-electrode voltage between the electrode 1and the workpiece 2 is detected by the detection value processingsection 23 (FIG. 31), and it is stored, as the discharge machiningvoltage, in the second memory section 222. The reference voltage isinputted through the input means 224 and stored in the second memorysection 222 in advance. In Step 54, the difference between the dischargemachining voltage and the reference voltage is compared with the rangeof difference Ve described above. When the difference is not within therange of difference Ve, in Step 55 the duration time measuring timer isreset. When the former is within the latter, in Step 56, the timer isallowed to count time. When, in Step 57, the content of the timerexceeds T, then it is regarded that the determination of the completionof the machining operation has accomplished (Step 58).

In the above-described embodiment, the range of difference Ve betweendischarge machining voltage and reference voltage, and the duration timeT within the range of difference Ve are employed as the machiningoperation completion determining parameters; however, they may bereplaced by an oscillating circulation frequency, or a range of distancefor back-and-forth movement by inter-electrode voltage servo, and aduration time in the range of distance. Furthermore, in theabove-described embodiment, a machining solution jet pressure, machiningarea, machining depth, and oscillation radius are employed as machiningenvironmental conditions determining factors; however, instead,oscillation configurations, electrode configurations and machiningconditions may be employed. The machining operation completiondetermining unit shown in FIG. 32 may be built in the electric dischargemachine NC unit.

In the above-described embodiment, the combination of the results by thelogic section 223 is carried out according to equations (1) and (2)which provide mean values; however, the composition may be achievedaccording to a variety of methods using weighted mean, maximum value,minimum value, etc.

The first memory section, the second memory section, and the logicsection may be formed according to the algorithm on inference which iswritten according to a fuzzy rule.

As is apparent from the above description, according to the invention, aplurality of machining environmental factors are detected and analyzedto obtain machining operation completion determining parameters suitablefor machining environmental conditions, so that the completion of themachining operation can be determined accurately according to thoseparameters, with a result that the workpiece is machined with highaccuracy. In the invention, unlike the prior art in which a uniformmachining operation completion determination is carried outindiscriminately, the machining time is effectively used; that is, themachining operation is carried out with high efficiency.

Furthermore, with the unit, the machining operation completiondetermining method is effectively practiced, the methods of detectingand analyzing the machining environmental factors are stored in thefirst memory section independently of the logic section, as a result ofwhich addition, modification and correction of the methods can beachieved with ease.

INDUSTRIAL APPLICABILITY

This invention can be widely applied to machining units such as electricdischarge machines.

We claim:
 1. An application control apparatus for a machining unit inwhich machining conditions can be changed during machining, comprising:aknowledge memory section for storing a plurality of different methods ofchanging machining states; a status memory section for storinginformation representing at least one of present machining states, pastmachining states and machining conditions; and an inference section forcombining a plurality of results obtained by said plurality of differentmethods, respectively, in accordance with the information stored in saidstatus memory section, thereby providing optimal machining states, eachof the stored plurality of different methods for changing machiningstates using information stored in said status memory section that isnot used by any other method to change the same machining state; saidmachining conditions of said machining unit being changed in accordancewith the optimal machining states.
 2. The application control apparatusas defined in claim 1, wherein said inference section includes means foraveraging the plurality of results obtained by said plurality ofdifferent methods to provide the optimal machining states.
 3. Anapplication control apparatus for a machining unit in which machiningconditions can be changed during machining, comprising:a knowledgememory section for storing a plurality of different methods of changingmachining states in a rule format including a front condition part whichdescribes a condition to be determined and a rear condition partdescribing contents to be carried out when said front condition part issatisfied and when said front condition part is not satisfied; a statusmemory section for storing information representing at least one ofpresent machining states, past machining states and machiningconditions; and an inference section for combining a plurality ofresults obtained by said plurality of different methods, respectively,in accordance with the information stored in said status memory section,thereby providing optimal machining states, each of the stored pluralityof different methods for changing machining states using informationstored in said status memory section that is not used by any othermethod to change the same machining state; said machining conditions ofsaid machining unit being changed in accordance with said optimalmachining states.
 4. The application control apparatus as defined inclaim 3, wherein said inference section includes means for averaging theplurality of results obtained by said plurality of different methods toprovide the optimal machining states.
 5. An application controlapparatus for a machining unit, comprising:a jump controlling unit forcontrolling a jumping operation of a machining electrode in a dischargemachining operation; a knowledge memory section for storing a pluralityof different methods for performing the jumping operation of saidmachining electrode; a status detecting unit for detecting machiningstatus data necessary for the stored methods; a status memory sectionfor storing information representing at least one of present machiningstates, past machining states and machining conditions detected by saidstatus detecting unit; and an inference section for combining aplurality of results obtained by said stored methods in accordance withthe information stored in said status memory section, thereby providingan optimal jumping operation, each of the stored different methods forperforming the jump operation using information stored in said statusmemory that is not used by any other method to change the same machiningstate.
 6. The application control apparatus as defined in claim 5,wherein said inference section includes means for averaging theplurality of results obtained by said plurality of different methods toprovide the optimal machining states.
 7. An application controlapparatus for a machining unit in which machining conditions can bechanged,said apparatus comprising:a first arrangement group comprising:a knowledge memory section for storing a plurality of different methodsof changing machining conditions; a state recognizing section fordetecting machining states and processing signals; a status memorysection for storing information representing at least one of machiningstates provided by said state recognizing section and set machiningconditions; and an inference section for obtaining optimal machiningconditions according to the information stored in said status memorysection and said methods stored in said knowledge section; and a secondarrangement group comprising:a time-series data recording section forrecording time-series data of said set machining conditions, saidmachining states provided by said state recognizing section andmachining condition changing operations performed by an operator; and aknowledge renewing section for extracting a machining method from saidrecorded time-series data, and for modifying said methods stored in saidknowledge memory section in accordance with said extracted machiningmethod; said first arrangement group operable for changing saidmachining conditions of said machining unit according to machiningconditions provided by said inference section; said first and secondarrangement groups are used to perform a machining operation whenperforming at least one of collecting and correcting machining methodsof an operator, said first and second arrangement groups also beingoperable to renew a method provided by said knowledge renewing sectionand stored in said knowledge memory section in accordance with, at leasta part of the machining conditions by said operator without use of anoutput of said inference section.
 8. A machining unit applicationcontrol unit for an electric discharge machine which has a detector fordetecting when a relative position of a machining electrode and aworkpiece is equal to a predetermined value and is controlled by anumerical control unit, comprising:a first memory section for storing aplurality of different methods for controlling a speed at which anelectrode and a workpiece move towards each other such that a relativeposition of said electrode and said workpiece can be detected, such thata frequency of the operation can be determined, and such that afterdetection of the relative position of said electrode and workpiece beingequal to a predetermined value, said electrode and workpiece are movedaway from each other, and then subsequently said electrode and workpieceare moved towards each other until said relative position is again equalto said predetermined value, said first memory section also storingaplurality of methods of determining a true detection position from afluctuation in the detection position; a second memory section forstoring information representing state data of an electrode and aworkpiece, and coordinates provided when the relative position of saidelectrode and said workpiece is equal to a predetermined value; and alogic section for combining a plurality of results obtained by saidplurality of methods stored in said first memory section in accordancewith the information stored in said second memory section, therebydetermining at least one of a speed and frequency of moving saidelectrode and said workpiece towards each other, and whether therelative position of said electrode and said workpiece is equal to saidpredetermined value.
 9. An electric discharge machining method in whichan electrode and a workpiece are moved relative to each other in such amanner that said electrode is moved towards said workpiece, and amachining operation is carried out while a distance between saidelectrode and said workpiece in a direction of movement of saidelectrode is being maintained constant by a servo control, and while oneof said electrode and workpiece is being oscillated in directionsperpendicular to the direction of movement of said electrode, saidmethod comprising:determining machining environmental factors includingmachining solution jet pressure, machining area, machining depth andoscillation radius to determine machining operation completiondetermining parameters, said parameters including a difference rangebetween a discharge machining voltage and a reference voltage, and atime duration within said range of difference; and determining when amachining operation completion operation is carried out in accordancewith whether said machining operation completion determining parametersare satisfied by detecting values provided during machining.
 10. Anelectric discharge machine in which an electrode and a workpiece aremoved relative to each other in such a manner that said electrode ismoved towards said workpiece, and a machining operation is carried outwhile a distance between said electrode and said workpiece in adirection of movement of said electrode is maintained constant by aservo control, and while one of said electrode and workpiece is beingoscillated in directions perpendicular to the direction of movement ofsaid electrode, said machine comprising:a first memory section forstoring a plurality of different methods for determining machiningenvironmental factors, said factors including machining solution jetpressure, machining area, machining depth and oscillation radius; asecond memory section for storing information representing at least oneof present machining states, past machining states and machiningenvironmental conditions; and a logic section for combining a pluralityof results obtained by said plurality of methods stored in said firstmemory section in accordance with the information stored in said secondmemory section, to obtain a machining operation completion determiningparameter, and to determine a machining operation completion accordingto said obtained parameter.